﻿namespace h4

{

    public class Circle

    {

        private double _radius;



        public Circle()

        {

        }



        public Circle(double radius)

        {

            _radius = radius;

        }



        public double Radius

        {

            get { return _radius; }

            set { _radius = value; }

        }



        public double CalculateCircumference()

        {

            return 2 * Math.PI * _radius;

        }



        public double CalculateArea()

        {

            return Math.PI * _radius * _radius;

        }



        public void DisplayInfo()

        {

            Console.WriteLine($"圆的半径: {_radius}");

            Console.WriteLine($"圆的周长: {CalculateCircumference():F2}");

            Console.WriteLine($"圆的面积: {CalculateArea():F2}");

            Console.WriteLine("------------------------");

        }

    }



    internal class Program

    {

        public static void Main(string[] args)

        {

            Circle circle1 = new Circle();

            circle1.Radius = 5;

            Console.WriteLine("第一个圆的信息:");

            circle1.DisplayInfo();



            Circle circle2 = new Circle(3.5);

            Console.WriteLine("第二个圆的信息:");

            circle2.DisplayInfo();



            circle2.Radius = 7;

            Console.WriteLine("修改半径后的第二个圆信息:");

            circle2.DisplayInfo();

        }

    }

}

